Find the nominal flexural strength $(M_n)$ and design strength $(M_n)$ of the reinforced concrete beam. The beam has a width of $b=12in.$ and an effective depth of $d=17\mathrm{.}5in.$ The beam is reinforced with four No$.8($No$.25)$ bars.

Concrete compressive strength: $f_c^{\text{'}}=4000$ psi

Steel yield strength: $f_y=60,000$ psi

Also, Determine the tensile strength of the concrete based on the given compressive strength and assess whether it meets the required design criteria for this beam.